The ancient Egyptian language was difficult to write and took a long time to learn. In the Middle East, the Semitic people used some simplified forms of Egyptian writing. They used simpler Egyptian symbols and matched them to the sound of a word. This is similar to the use of Chinese characters to write the sounds for foreign words, for example bus (巴士). One of the more advanced Semitic tribes were the Phoenicians. They were creating great trading businesses around the Mediterranean Sea. They needed a cheaper and easier way to write. So they took the bits and pieces of the simplified Egyptian-Semitic writing and put it together into the first alphabet. All other Western alphabets are descended from this alphabet.
The Phoenician alphabet had problems. For example, there were no vowels. The Greeks borrowed the Phoenician alphabet, but needed vowels to use it. So the Greeks rewrote it to match their own language's needs creating the Greek alphabet. All European writing systems are descended from the Greek alphabet. The word alphabet, comes from the first two letters of the Greek alphabet, alpha and beta.
The Greek alphabet was later borrowed and modified by the Romans and Etruscans. They created the Latin alphabet. Everyone reading this article will recognise the Latin alphabet. (A B C D E F Z H I K L M N O P Q R S T V X) The letter order is from the Phoenician alphabet.
Old English was originally written in a very different script called runic. (See: John Larrysson Column: Ye and the Lost Letter Publishing Date: 2012/12/19) More than a thousand years ago Old English was slowly growing out of its uncivilised barbarian history. At the time, most books were written in Latin. So English, and some other barbarian languages, got clumsily rewritten in the Latin alphabet, with very few changes. This was a big problem because English, as a German dialect, is very different from Latin. The alphabet did not match. Latin had no letters for some sounds. To solve this problem, the extra sounds were written with two letters to represent one sound. As an exercise in phonology, a teacher might ask their more advanced students to try to figure out what the extra sounds were.